Various mechanisms have been proposed for use in mounting a door of a vessel for opening and closing movements in a manner requiring minimum floor space in front of the vessel and/or permitting minimum clearance distances to be maintained between obstructions and the front or sides of such vessel. As by way of example, reference may be made to prior U.S. Pat. Nos. 2,507,522; 2,529,478; 2,601,566; 2,639,144; 2,639,601; 2,923,430; and 3,067,986.